Production of vinyl oxazoline esters

ABSTRACT

1. IN A PROCESS FOR THE PRODUCTION OF A VINYL OXAZOLINE CORRESPONDING TO THE FORMULA   2-(CH2=C(-R)-),4-R1,4-R2-2-OXAZOLINE   WHEREIN R IS AN ALKYL OR ALKENYL GROUP OF FROM 1 TO 20 CARBON ATOMS AND R1 AND R2 ARE METHYL, ETHYL OR THE GROUP   R-CH2-COO-CH2-   AND CAN BE THE SAME OR DIFFERENT, BY REACTING AN OXAZOLINE CORRESPONDING TO THE FORMULA   2-(R-CH2-),4-R1,4-R2-2-OXAZOLINE   WITH AN ALKANOL SOLUTION OF FORMALDEHYDE IN A MOLE RATIO OF FROM 1-8 OF SAID FORMALDEHYDE TO 1 OF SAID OXAZOLINE, AT AN ELEVATED TEMPERATURE FOR A PERIOD OF TIME SUFFICIENT TO EFFECT PRODUCTION OF SAID VINYL OXAZOLINE, AND THEREBY FORMING WATER OF REACTION, AND SEPARATING SAID WATER BY DISTILLATION, THE IMPROVEMENT COMPRISING THE STEP OF RAPIDLY ADDING SAID FORMALDEHYDE SOLUTION TO SAID OXAZOLINE AT A TEMPERATURE OF 185-190*C. WHILE MAINTAINING THE TEMPERATURE AT NOT LESS THAN 185*C.

United States Patent Oifice 3,839,350 Patented Oct. 1, 1974 US. Cl.260307 F 1 Claim ABSTRACT OF THE DISCLOSURE An improved process for theproduction of a vinyl oxazoline or a vinyl oxazoline ester bycondensation of an oxazoline or an oxazoline ester with a solution offormaldehyde in a lower al kanol at a temperature of 185- 190 C. andmaintaining the temperature at 185190 C. for a period of time sufficientto effect dehydration of the condensation product.

This is a continuation, of application Ser. No. 46,476, filed June 15,1970, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to the production ofoxazoline derivatives. In a particular aspect, it relates to theproduction of vinyl oxazolines and vinyl oxazoline esters by thecondensation of formaldehyde with an oxazoline or oxazo line ester.

'It is known in the art to prepare vinyl oxazolines and vinyl oxazolineesters by condensing an oxazoline corresponding to formula I:

RC Hg (I; wherein R is an alkyl or alkenyl group of from 1 to 20 carbonatoms and R and R are methyl, ethyl or CH1-OCCHQR,

and can be the same or different, with formaldehyde in about a 1:2 moleratio and at a temperature of 100125 C. in the presence of an inertatmosphere, such as by sparging nitrogen through the reaction mixture.Previously, paraformaldehyde has been used as the formaldehyde source,and the temperature was held in the foregoing range until theparaformaldehyde had dissolved, thereby forming a bis-hydroxymethyladdition compound. The temperature was then raised to 200 C. or more toeffect dehydration and formation of the vinyl compound. Also it is knownthat the best yields are obtained when the reaction mixture is heatedrapidly, e.g. at 12/min., to 185 C. then held at that temperature fordehydration to be completed.

Products of this type, especially those from unsaturated fatty acids,are useful as synthetic vehicles for the formulation of both baking typeand air-drying paints, varnishes and other coatings.

This process has been very successful on a small scale, but the rapidrise in temperature proved difiicult to achieve when large volumes ofmaterials were used. Consequently conversion to the vinyl oxazoline wascomparatively low. By-products and incomplete conversions lead tovariations in the performance of the dried coatings in which the vinyloxazolines are used as the vehicle. Separation of the objectionablefractions is diflicult to achieve because, like the principal product,they are high-boiling and their boiling points lie close together.

By-products include a divinyl compound haaving a vinyl group on thea-carbon of the 4-acyloxy group, if any, Compounds of this type areobjectionable in coating vehicles because they tend to formcross-linking polymers which are hard and poorly soluble in the usualsolvents.

Other objectionable components include 2-(1-ethenyl alkyl oralkenyl)-4-alkyl or hydroxymethyl 4 hydroxymethyl oxazolines resultingfrom hydrolysis of the ester, unreacted ester oxazoline startingcompound, unconverted condensation products, and color bodies. It isdesirable to minimize such components both individually and colleclivelyto obtain the full advantages of the synthetic vehicles.

SUMMARY OF THE INVENTION It is an object of this invention to provide animproved process for the production of oxazoline derivatives.

It is another object of this invention to provide an im proved processfor the production of 2-(l-ethenyl alkyl or alkenyl) oxazolines oroxazoline esters of relatively high ethenyl (vinyl) content.

A third object of this invention is a method for the production ofcompositions having a low proportion of unreacted oxazoline or oxazolineester, unconverted formaldehyde condensation product, vinyl oxazolinealcohol resulting from hydrolysis of the vinyl oxazoline ester, anddivinyl compounds.

It is the discovery of this invention that vinyl oxazolines and vinyloxazoline esters corresponding to the following formula II, can beproduced in much higher purity than by the prior processes:

DETAILED DISCUSSION In carrying out the process of this invention, anexamline corresponding to formula I set forth above is charged to areaction vessel equipped with an agitation means, a temperature sensingdevice and a decanter head with a reflux condenser. A polymerizationinhibitor, about 0.01% to 0.1% by weight, is added when desired, and ispreferred when R in the foregoing formula contains less than 10 carbonatoms. The mixture is then heated with agitation to When the pottemperature has reached 185 C., the formaldehyde solution is addedincrementally but as rapidly as possible without causing the temperatureto fall below 185 C. After formaldehyde addition is complete, heating iscontinued at 185190 until elimination of water of reaction is complete,e.g. for about 15-45 min.

When water of reaction is no longer being eliminated, the crude product,the vinyl oxazoline, is allowed to cool. It is generally suitable foruse as is or the lower molecular Weight products can be vacuum distilledto obtain a purified material.

The oxazoline starting materials represented by formula I as used in thepractice of this invention are commercially available or can be preparedby any suitable process, many of which are known. The commerciallyavailable materials are generally satisfactory. Preferably, they are ofgood quality.

The formaldehyde used in the practice of this invention is supplied as anon-aqueous, but not necessarily anhydrous, solution. A suitable solventis one which is miscible but not reactable with oxazoline. Gaseousformaldehyde can also be used when convenient. Preferably theformaldehyde is supplied as a solution in an alkanol of from 1-4 carbonatoms, e.g. in methanol, ethanol, 2- propanol or butanol. Thesesolutions are commercially available and the usual commercial productsare suitable. The formaldehyde is used in a mole ratio of from about l8per mole of oxazoline.

As set forth above, when R contains less than 10 carbon atoms, fromabout 0.01% to about 1% of a polymerization inhibitor is employed in thedehydration step. Suitable inhibitors include di-beta-naphthol,hydroquinone, p-hydroxydiphenylamine, N,N-diphenylphenylenediamine, 2,-di-tert.-butylhydroquinone, trinitrotoluene, copper carbonate,methylene blue and butylated hydroxytoluene.

The invention will be better understood with reference to the followingexamples. They are intended only to further illustrate the invention andit is not intended that the invention be limited thereby.

Example 1 An oxazoline diester, 1 mole, prepared from tall oil fattyacids and tris(hydroxymethyl)aminomethane was charged to a reactionvessel equipped with an agitation means, and a distillation column witha take-off head and was heated under an atmosphere of nitrogen to 185 C.Formaldehyde, 2 moles, dissolved in methanol (55% by wt. solution) wasadded gradually to the heated oxazoline, but as rapidly as possiblewithout cooling the reaction mixture below 185 About 1 hour Wasrequired. The heating was continued for about 45 min. during which timemethanol, formaldehyde and water of reaction were collected in thetake-off head.

The product was cooled under the inert atmosphere to room temperature.It had a color of '9, Gardner, and a viscosity of E, Gardner. The vinyldiester content as determined from the infrared absorption spectrum was2.28 times as great as the vinyl content of an oxazoline prepared by theprior process using paraformaldehyde in place of the methanolicsolution.

Example 2 The experiment of Example 1 was repeated in all essentialdetails except that the oxazoline employed was the mono-ester preparedfrom 2-amino-2-ethyl-1,3-propanediol and pelargonic acid. The resultingproduct had a very high vinyl oxazoline ester content compared with thatobtained by the prior process. The viscosity was D+ and the color 17.

Example 3 The experiment of Example 1 was repeated in all essentialdetails for 7 runs, except that the reaction temperature was held at 190C. and in runs 2 and 3 the formaldehyde was supplied in isobutyl alcoholand nbutanol, respectively, instead of methanol. Also the mole ratio offormaldehyde to axazoline was varied. The vinyl content in the tablebelow is expressed as the ratio of the vinyl content of the productobtained by the new process to the statistically standard vinyl contentof the product obtained by the prior process. The data are summarized inthe following table:

' Moles HCHO to est 2 2 2 4 4 8 8 Color 10 9 8 14 13 12 10 Visc0sity G-HD D G F-G G-H I Heating time, Im'n. 45 45 45 45 45 15 Vinyl content 2.10p 2. 75 2. 34 2.09 1. 87 2. 34 2. 54

1 After formaldehyde addition is complete. 2 None.

Example 4 The experiment of Example 1 is repeated except that 2 ethyl 4methyl-4-propionyloxymethyl-Z-oxazoline, 4 moles, is employed as theoxazoline. A high yield of 2-isopropenyl-4-methyl-4-propionyloxymethyl 2oxazoline is obtained.

Example 5 The experiment of Example 1 is repeated except that2-ethyl-4,4-bis (propionyloxymethyl)-2-oxazoline, 4 moles, is employedas the oxazoline. A high yield of 2-isopropenyl 4,4bis(propionyloxymethyl)-2-oxazoline is ob tained.

Example 6 The experiment of Example 1 is repeated except that2-heptadecyl-4-methyl-4-octadecanoyloxymethyl 2 oxazoline, 4 moles isemployed as oxazoline. A high yield of 2(l-ethenylheptadecyl)-4-methyl-4-octadecanoyloxy methyl-2-oxazoline isobtained.

Example 7 The experiment of Example 1 is repeated in all essentialdetails except that 2-heptadecenyl-4,4-dimethyl-2- oxazoline, 4 moles,is employed as the oxazoline. A high yield of2-(l-ethenylheptadecenyl)-4,4-dimethyl-2-oxazoline is obtained.

What is claimed is:

1. In a process for the production of a vinyl oxazoline corresponding tothe formula wherein R is an alkyl or alkenyl group of from 1 to 20carbon atoms and R and R are methyl, ethyl or the group -CH,-o-("J-oHiRo and can be the same or different, by reacting an oxazolinecorresponding to thhe formula R1 H2C+R /N R H. with an alkanol solutionof formaldehyde in a mole ratio of from 1-8 of said formaldehyde to 1 ofsaid oxazoline, at an elevated temperature for a period of timesufficient to effect production of said vinyl oxazoline, and therebyforming water of reaction, and separating said water by dlSt11latlOI1,the improvement comprising the step of rapidly adding said formaldehydesolution to said oxazoline at a temperature of 190 C. While maintainingthe temperature at not less than 185 C.

References Cited UNITED STATES PATENTS 3,248,397 4/1966 Purcell 260-3073,535,332 10/1970 Runge et a1 260307 3,652,513 3/1972 Gagliardi 26080.3

RAYMOND V. RUSH, Primary Examiner

1. IN A PROCESS FOR THE PRODUCTION OF A VINYL OXAZOLINE CORRESPONDING TOTHE FORMULA